Long-haul optical telecommunication networks currently utilize high performance optoelectronic components such as lasers and photodetectors that are coupled to single mode optical fibers. Although presently these components are expensive, their effective cost is low since they are shared among thousands of customers. The economic situation is beginning to change as telephone companies extend the optical fiber network directly to the home. Expansion of optical fiber into the local loop will require several optoelectronic, electronic and fiber components for each customer. This situation will impose significant demands on realizing optoelectronic components that can be manufactured at low cost.
The cost of all optoelectronic (and most electronic) components is dominated by the package rather than the device itself. For example, the alignment and attachment of an optical fiber pigtail and a diode laser in an optical transmitter are the most costly packaging steps. The cost of this operation for a single transmitter will be multiplied for applications involving the use of many parallel transmitters in the local loop in which arrays of lasers are coupled to arrays of single mode fibers.
In addition to telecommunication applications, the issue of low cost optoelectronic components will also determine the economic viability of other applications of optoelectronic technology such as the use of optical interconnects in high speed computers.
The conventional approach to attachment of a fiber pigtail to a diode laser package is a labor intensive process. The laser must first be die and wire bonded to the package so that it can be biased to its normal operating condition. The input end of the fiber pigtail is then mechanically manipulated in front of the laser active region while the optical output of the fiber is monitored until optimal coupling is achieved. A single mode fiber (9 .mu.m core diameter) must be positioned with submicron accuracy in front of the laser emitting region, which typically has dimensions of about 2.times.0.2 .mu.m. Once the maximum coupling has been obtained, the fiber is bonded into place. This approach requires either human interaction or expensive equipment that automatically dithers the fiber to its optimal position. An additional disadvantage is that the fiber can move from its optimal position during the process of attachment to the package due to the motion of bonding materials (such as epoxy shrinkage) or during the use of the laser in the field. This conventional alignment technique will be significantly more complicated as the need develops for the coupling of laser arrays to fiber arrays.
The alignment of fiber arrays to laser arrays has been reported for the case of multimode fibers (50 .mu.m core diameter) by Jackson et al. in "Optical fiber coupling approaches for multichannel laser and detector arrays," SPIE Vol. 994 (1988). Although V-grooves were used to position fibers relative to the lasers in the vertical z-direction, active alignment was required to position the fibers in the lateral x and y directions. The present invention eliminates all active alignment procedures and provides alignment accuracy that will be adequate for passive alignment of single-mode fibers.